Another Bow Thruster Question

[Baggy]

My new set up is a Battery close to the Bow Thruster fed by a charge cable from the Starter battery and Alternator when engine is on

The charge cable is 16mm2 on a 8 mtr run rated at 50 amps

I have fitted 50 amp fuse at BT batt end, and a 50amp cct breaker at Starter Batt end, via a batt isolator switch

The trouble is I keep blowing the 50 amp fuse, probably due to the BT batt dragging in high amps from the Starter batt/ alternator

Is their a way of restricting the Amp flow to BT batt to say 30/40 amps,
other than using a B to B charger ?

 

[Catalina36]

One option would be to replace the 16mm2 cable with say 35mm2 or 50mm2 which would permit a larger fuse to be fitted and allow the starter battery/alternator to assist in running the thruster, which it apparently wants them to do. How large is the BT battery?

 

[rogerthebodger]

What bow thruster do you have You did not specify in your first post on the other thread

 

[Baggy]

BT batt is 65AH high cranking battery, as per installation guide

I,m thinking even with running a high amp rated cable, which I do not want to do
the BT batt going flat could still ask very high current rate,s from the Starter batt

Just want a simple device to restrict high ampage flow, if there is one

 

[Baggy]

What bow thruster do you have You did not specify in your first post on the other thread

The Bow Thruster is a Max Power CT 45 3.4 Kw

 

[pvb]

What bow thruster do you have You did not specify in your first post on the other thread

In the other thread, he said it was a CT45.

Bow Thruster Circuit Breaker Question

 

[pvb]

Is their a way of restricting the Amp flow to BT batt to say 30/40 amps,
other than using a B to B charger ?

Not really, you could fit a thicker cable, or buy a B-to-B charger.

 

[Baggy]

Oh gawd, more expense

Any votes for a Votronic 30amp B to B charger
which may or may not need connecting to the C+, on the Alternator

 

[Catalina36]

I guess it rather depends upon how long you're running the thruster for. 3.4kw on 12 volts is around 300 amps which is going to deplete a 65 AH battery if used for more than the few second bursts thrusters are usually used for. You indicated in the other thread that you'd been running it for longer to test it, but for how long and to test what exactly? You wouldn't crank your engine for minutes at a time and not expect the battery to go flat and start looking for back-up.

 

[pvb]

Oh gawd, more expense

Any votes for a Votronic 30amp B to B charger
which may or may not need connecting to the C+, on the Alternator

Isn't that unit about £150? How much would thicker cable cost?

 

[rogerthebodger]

In the other thread, he said it was a CT45.

Bow Thruster Circuit Breaker Question

To me a CT45 is a stainless steel firearm so I needed the OP to confirm which Bow thruster he has.

The voltage rating would also help the OP with his issue.

The connecting 2 battery banks together and having 50 Amps flow between the 2 seems very high unless one if faulty in some way.

 

[pvb]

To me a CT45 is a stainless steel firearm so I needed the OP to confirm which Bow thruster he has.

The voltage rating would also help the OP with his issue.

The connecting 2 battery banks together and having 50 Amps flow between the 2 seems very high unless one if faulty in some way.

The OP gave the thruster type in the post I linked to. I believe you'll find that the MaxPower CT45 is a 12v thruster.

 

[rogerthebodger]

The OP gave the thruster type in the post I linked to. I believe you'll find that the MaxPower CT45 is a 12v thruster.

Thanks for the confirmation.

This means the current consumption is just under 300 Amps as Catalina36 said.

If the fuse blows when the bow thruster is operated it could be the the 65Ah battery connection is not right and all the current is being drawn fro the engine start batteries or the 65Ah battery which is a bit small for that size of BT could be depleting quickly and the majority of the current is then supplied by the engine battery so the 50 Amp Fuse would blow.

Your B to B charger would could prevent that but the BT would stop after a very little operating time of may be a few minutes.

I drive mine from a battery bank of over 1200 Ah being 12 x 105 Ah

 

[C08]

I would have expected that the circa 300A demanded by the BT would be split fairly evenly apart from a little volt drop on the charging cable so I would expect that to blow a 50A fuse.

 

[TernVI]

You could fit a relay which switches off when the thruster is used.
There are various electronic means of limiting the current.

The non-obvious solution is to fit much thinner cable, its resistance will limit the current but it will still charge the bow battery OK.
You have to do the maths this only works if the length is enough.

 

[TernVI]

Thanks for the confirmation.

This means the current consumption is just under 300 Amps as Catalina36 said.

If the fuse blows when the bow thruster is operated it could be the the 65Ah battery connection is not right and all the current is being drawn fro the engine start batteries or the 65Ah battery which is a bit small for that size of BT could be depleting quickly and the majority of the current is then supplied by the engine battery so the 50 Amp Fuse would blow.

Your B to B charger would could prevent that but the BT would stop after a very little operating time of may be a few minutes.

I drive mine from a battery bank of over 1200 Ah being 12 x 105 Ah

The alternator will chuck out its rated current into say 14V before anything comes out of the start battery.
A Bto B charger is the most elegant solution IMHO.

 

[rogerthebodger]

The alternator will chuck out its rated current into say 14V before anything comes out of the start battery.

That's true if the engine is running at such a speed to allow the alternator to generate the required current.

It the engine is running and is connected to the engine start battery the current flow down the interconnection cable will cause the 50 Amp fuse to blow.

 

[pvb]

Just want a simple device to restrict high ampage flow, if there is one

OK, maybe the simplest device would be an echo charger, such as this - Votronic 12V StandBy Charger (Trickle Charger)

It should recharge your thruster battery when charging voltage is present, and shouldn't let the thruster battery drag current from the starter battery.